Low self-shrinking hydraulic composition

Abstract

To provide a hydraulic composition with low autogenous shrinkage strain even when a large amount of blast furnace slag fine powder is used.SOLUTION: A low autogenous hydraulic composition includes Portland cement, blast furnace slag fine powder, quick lime and anhydrous gypsum. In the composition, for a total of 100 pts.mass of the Portland cement and the blast furnace slag fine powder, the blast furnace slag fine powder is 60-80 pts.mass, and for 100 pts.mass of the blast furnace slag fine powder, the quick lime is 1.4-4.2 pts.mass in terms of CaO in the quick lime and the anhydrous gypsum is 0.2-2.0 pts.mass.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a hydraulic composition which contains a large amount of ground granulated blast furnace slag and yet has a small autogenous shrinkage strain. [Background technology]

[0002] In recent years, in order to reduce environmental impact, the use of blended cements containing large amounts of fly ash and blast furnace slag has been considered as an alternative to Portland cement, which emits large amounts of carbon dioxide during its production. In particular, the use of blast furnace cement type C (mix ratio of over 60% to 70% or less) has attracted attention and is currently being used in a variety of structures. For example, the Japan Society of Civil Engineers has published "Design and Construction Guidelines (Draft) for Concrete Structures Using Large Amounts of Admixtures," and positive efforts are being made across the industry. However, there are concerns that mortar and concrete that use large amounts of ground granulated blast furnace slag may increase autogenous shrinkage strain.

[0003] To address these concerns, methods include reducing the fineness of the ground granulated blast furnace slag, using an expansion agent or shrinkage reducing agent as an admixture, or using other cement. Patent Document 1 reports a technology that combines low-heat Portland cement and ground granulated blast furnace slag to reduce adiabatic temperature rise and autogenous shrinkage strain. Patent Document 2 states that autogenous shrinkage strain can be reduced by adding fly ash, ground granulated blast furnace slag, and gypsum. Patent Document 3 describes concrete containing Portland cement, ground granulated blast furnace slag, and quicklime-based expansive material, in which the Blaine specific surface area of ​​the quicklime-based expansive material is 4500 cm 2 / g or more, it is said that autogenous shrinkage strain can be reduced. Also, according to Patent Document 4, it is said that autogenous shrinkage strain can be reduced by using ground granulated blast furnace slag in combination with a shrinkage reducing agent. Furthermore, according to Patent Document 5, it is said that when the Blaine specific surface area of ​​ground granulated blast furnace slag is 1500 to 3600 cm 2 / g and the inclusion of 3 to 35 parts by weight of an expansion component (expansion material) per 100 reduces autogenous shrinkage strain. According to Patent Document 6, autogenous shrinkage can be reduced by forming a carbonated layer on the surface of ground granulated blast furnace slag particles. According to Patent Document 7, the addition of gypsum and calcium carbonate to ground granulated blast furnace slag can reduce autogenous shrinkage strain. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-62234 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-43519 [Patent Document 3] Japanese Patent Application Publication No. 2019-147699 [Patent Document 4] Japanese Patent Application Laid-Open No. 2003-95714 [Patent Document 5] Japanese Patent Application Laid-Open No. 2007-217197 [Patent Document 6] Japanese Patent Application Laid-Open No. 2014-189423 [Patent Document 7] Japanese Patent Application Laid-Open No. 2016-23105 Summary of the Invention [Problem to be solved by the invention]

[0005] However, each of the above-mentioned measures to prevent autogenous shrinkage has its own issues. Specifically, 1) changing the type of cement reduces strength development, 2) adding gypsum can be expected to expand but reduces strength development, 3) using expansive additives and shrinkage-reducing agents increases costs, 4) carbonation of particles requires specialized equipment, and 5) the inclusion of calcium carbonate promotes carbonation in mortar and concrete made with blast furnace slag. Therefore, an object of the present invention is to provide a hydraulic composition that exhibits small autogenous shrinkage strain even when a large amount of ground granulated blast furnace slag is used. [Means for solving the problem]

[0006] As a result of extensive research into hydraulic compositions containing a large amount of ground granulated blast furnace slag, the inventors discovered that the above-mentioned problems can be solved by blending quicklime and anhydrous gypsum with ground granulated blast furnace slag in a predetermined ratio, and thus completed the present invention. That is, the present invention provides the following [1] and [2]. [1] A hydraulic composition containing Portland cement, ground granulated blast furnace slag, quicklime and anhydrous gypsum, characterized in that the ground granulated blast furnace slag is 60 to 80 parts by mass per 100 parts by mass of the total of the Portland cement and the ground granulated blast furnace slag, and the quicklime is 1.3 to 4.2 parts by mass, calculated as CaO in the quicklime, and the anhydrous gypsum is 0.2 to 2.0 parts by mass per 100 parts by mass of the ground granulated blast furnace slag. [2] Autogenous shrinkage strain at 28 days is 0 to 100 × 10 -6 2. A hardened product of the low self-shrinkage hydraulic composition according to claim 1, wherein: [Effects of the Invention]

[0007] Even when a large amount of ground granulated blast furnace slag is used, a hydraulic composition with small autogenous shrinkage strain can be obtained, which makes it possible to provide mortar and concrete that are free from cracks due to autogenous shrinkage and have an excellent effect of reducing environmental impact. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, an embodiment of the present invention will be described. The hydraulic composition of the present invention is a hydraulic composition containing Portland cement, ground granulated blast furnace slag, quicklime, and anhydrous gypsum, characterized in that the amount of ground granulated blast furnace slag is 60 to 80 parts by mass per 100 parts by mass of the total of the Portland cement and the ground granulated blast furnace slag, and the amount of the quicklime is 1.5 to 4.4 parts by mass, calculated as CaO in the quicklime, and the amount of the anhydrous gypsum is 0.2 to 2.0 parts by mass per 100 parts by mass of the ground granulated blast furnace slag.

[0009] The Portland cement used in the present invention includes various types of Portland cement, such as normal, high-early-strength, and moderate-heat. Any one type of Portland cement can be used, but two or more types of cement can also be used in combination. Normal Portland cement is preferred for its versatility.

[0010] The ground granulated blast furnace slag used in the present invention is a fine powder obtained by pulverizing granulated blast furnace slag produced in the pig iron manufacturing process, and it is preferable to use ground granulated blast furnace slag for concrete specified by the Japanese Industrial Standards. The fineness of the ground granulated blast furnace slag is 3000 to 8000 cm in terms of Blaine specific surface area. 2 / g is preferred, and 4000 to 6000 cm 2 / g is more preferred.

[0011] The content of ground granulated blast furnace slag in the hydraulic composition of the present invention is 60 to 80 parts by mass per 100 parts by mass of the total of Portland cement and ground granulated blast furnace slag. Note that blast furnace cement can also be used as the Portland cement and ground granulated blast furnace slag in the present invention. Blast furnace cement is produced by mixing and grinding Portland cement clinker and blast furnace slag, or by mixing Portland cement and ground granulated blast furnace slag.

[0012] The quicklime used in the present invention may be industrially produced industrial quicklime, but any quicklime containing free quicklime (f-CaO) as the main component can be used. The CaO content in the quicklime is preferably 80% by mass or more, more preferably 85% by mass or more, and even more preferably 90% by mass or more. In addition, the free quicklime content in the quicklime is preferably 60% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more. The fineness of the quicklime is such that the Blaine specific surface area is 2000 cm 2 / g or more is preferred.

[0013] The content of quicklime is 1.4 to 4.2 parts by mass, calculated as CaO in quicklime, per 100 parts by mass of ground granulated blast furnace slag. If the content is less than 1.4 parts by mass, there is a risk of cracking due to autogenous shrinkage. If the content exceeds 4.2 parts by mass, there is a risk of hair cracks occurring on the surface of the hardened body. A content of 1.5 to 4.0 parts by mass is more preferable.

[0014] The anhydrous gypsum used in the present invention may be natural anhydrous gypsum or various anhydrous gypsums that are industrially produced or produced as by-products. Examples of industrially produced anhydrous gypsum include hydrofluoric gypsum and phosphate gypsum. The fineness of the anhydrous gypsum is 5000 to 9000 cm in terms of Blaine specific surface area. 2 / g is preferred, and 6000 to 8000 cm 2 / g is more preferred.

[0015] The content of anhydrous gypsum is 0.2 to 2.0 parts by mass relative to 100 parts by mass of ground granulated blast furnace slag. If it is less than 0.2 parts by mass, there is a risk of reduced fluidity due to false setting. If it exceeds 2.0 parts by mass, there is a risk of reduced strength development. 0.4 to 1.5 parts by mass is more preferable.

[0016] In addition, the hydraulic composition of the present invention can contain aggregate. As the aggregate, fine aggregate and coarse aggregate used in the production of ordinary mortar concrete can be used. Examples of such fine aggregate and coarse aggregate include river sand, sea sand, mountain sand, crushed sand, artificial fine aggregate, slag fine aggregate, recycled fine aggregate, silica sand, river gravel, land gravel, crushed stone, artificial coarse aggregate, slag coarse aggregate, recycled coarse aggregate, etc. The blending amount of aggregate is 700 to 1400 kg / m 3 is preferable, and more preferably 800 to 1000 kg / m 3 is preferred.

[0017] The hydraulic composition of the present invention may also contain aggregate. The water used is not particularly limited, and tap water or the like may be used. The amount of water (unit water amount) is 100 to 300 kg / m 3 is preferable, and more preferably 150 to 250 kg / m 3 is preferred.

[0018] In addition to the above-mentioned components, various admixtures (materials) may be added to the hydraulic composition of the present invention as needed, provided that the features of the present invention are not impaired. Examples include water-reducing agents, high-performance water-reducing agents, air-entraining agents, air-entraining water-reducing agents, high-performance air-entraining water-reducing agents, set regulators, hardening accelerators, thickeners, shrinkage-reducing agents, cement polymers, waterproofing agents, rust inhibitors, antifreeze agents, water-retaining agents, pigments, efflorescence inhibitors, foaming agents, antifoaming agents, water-repellents, and fibers.

[0019] The hydraulic composition of the present invention has a small autogenous shrinkage strain despite containing a large amount of ground granulated blast furnace slag. When evaluated as a mortar, the autogenous shrinkage strain at 28 days is 0 to 100 × 10 -6 A cured body of the above formula can be obtained. [Example]

[0020] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[0021] (Materials used) The materials used in the examples are shown in Table 1.

[0022] [Table 1]

[0023] (Mortar mix) The mortar mix is ​​shown in Table 2. In Table 2, CaO / BFS represents the CaO content (parts by mass) in quicklime per 100 parts by mass of ground granulated blast furnace slag, and CaSO4 / BFS represents the anhydrous gypsum content (parts by mass) per 100 parts by mass of ground granulated blast furnace slag.

[0024] [Table 2]

[0025] (Evaluation test) An autogenous shrinkage test was conducted according to JIS A 6202 "Mortar Restrained Expansion Test." Mortar was molded into a mortar restraining bar and demolded after one day of age. The demolded specimens were sealed and cured with aluminum tape and measured up to 28 days of age. The effectiveness was judged as "×" if a negative autogenous shrinkage strain was measured after 28 days of age, and "○" if a positive autogenous shrinkage strain was measured. The compressive strength of the material was measured at 28 days old according to JIS R 5201 "Compressive Strength Test for Mortar." The effect was judged as "×" if the strength was lower than that of mortar without added quicklime or anhydrous gypsum, and "○" if the strength was the same or higher.

[0026] (Test results) The test results are shown in Table 3. It is clear that the set product of the hydraulic composition of the present invention has small autogenous shrinkage strain, and no decrease in compressive strength was observed.

[0027] [Table 3]

Claims

1. A hydraulic composition comprising Portland cement, ground granulated blast furnace slag, quicklime and anhydrous gypsum, wherein the ground granulated blast furnace slag is 60 to 80 parts by mass per 100 parts by mass of the total of the Portland cement and the ground granulated blast furnace slag, the quicklime is 1.4 to 4.2 parts by mass, calculated as CaO in the quicklime, and the anhydrous gypsum is 0.2 to 2.0 parts by mass per 100 parts by mass of the ground granulated blast furnace slag, and the anhydrous gypsum has a Blaine specific surface area of ​​5,000 to 9,000 cm2 / g as the fineness of the anhydrous gypsum.

2. Autogenous shrinkage strain at 28 days is 0 to 100 x 10 -6 2. A hardened product of the low self-shrinkage hydraulic composition according to claim 1,

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